High voltage electrical distribution grid networks provide the means for transferring electrical energy from the generator source to distribution centers, to feeder networks and, eventually, to individual consumers.
Typically, the high voltage distribution networks are relatively stable in their construction and configuration. Such networks are planned in advance to provide electrical energy from generators to the distribution centers to the residential and commercial customers. Distribution centers and feeder networks, therefrom, however, may have configurations that change in response to specific conditions. For example, a distribution center may be configured or reconfigured to accommodate additional service areas or customers within a known service area. Similarly, the high voltage network configuration may change with the addition of new generation capacity and/or new distribution centers. Network switching in order to accommodate maintenance of a circuit element or to isolate a faulted circuit element will likewise change the configuration of the system.
Generally, the characteristics of the networks are determined or estimated when the network is created. In accordance with known procedures, the determined or estimated characteristics of the network are generally formulated when the network is installed and not updated as changes to the system are made. In one aspect, an impedance ratio, referred to as an SIR, may be formulated based on models of the network characteristics between distribution centers, or represent actual measurement of network characteristics or be a combination of measured values and network models.
These characteristics are used in many cases as reference values that may be used in monitoring the health of the system or in determining actions to be performed. When the measured values exceed or fall outside of tolerable ranges, an error may be declared and one or more safety mechanisms within the network may be triggered. For example, if a circuit failure occurs, one or more measured values may fail outside a desired range and safety relays may be triggered to isolate the failure from the network.
For example, in the case of a circuit failure, to prevent the failure from being propagated through the network, a distribution center may include safety devices that determine the electrical distance of the failure from the safety device. If the failure is determined to be within a coverage region, based on a determined distance between the failure and the distribution, the distribution center may cause one or more actions to occur to isolate the failure from the network.
However, the distance determination is based in part of the estimated network characteristics and as the network is updated, the estimated network characteristics are not representative of the actual network characteristics. Thus, the determined distance measurement to the detected failure may be incorrectly determined and a distribution center not affected by the failure may initiate actions that are unnecessary.
Further still, as the actual network characteristics change, the tolerance values, which are based on the initially estimated values, and used to monitor the network may no longer be appropriate.
Hence, there is a need in the industry for a method to determining network characteristics as the network is changed and to use this information to adapt tolerance values accordingly.